Problem solving based on experience of working with other problems which share some characteristics of the current problem, but for which no algorithm is known. Good heuristics can reduce the time needed to solve problems by recognizing which possible approaches are unlikely to be successful. George Polya brought the notion of heuristics to a wide audience through his book How To Solve It. The second edition was published in 1957 and is still in print half a century later.

(psychology, by extension) Simple, efficient rules which people often use to form judgments and make decisions.

(engineering, by extension) Experience-based methods used to reduce the need for calculations pertaining to equipment size, performance, or operating conditions.